A system that displays a 3D image by capturing the image of the same subject using two video cameras disposed in the left and right sides and outputting the left and right images at the same time has been developed. However, if such two video cameras are used, the size of an apparatus including the cameras is increased and, therefore, the apparatus is not practical. Additionally, in general, the baseline extending between the two cameras, that is, a distance between two eyes of the 3D camera is set to about 65 mm, which corresponds to the distance between the eyes of a person. In such a case, the parallax is increased when a zooming operation is performed on the video image, and the human eye system is forced to perform information processing that is not performed as usual. Accordingly, eye fatigue occurs. In addition, if the right and left images are directly overlaid and are looked at, the image is doubly-blurred and, therefore, an unnatural video is generated. Note that L and R represent the positions of the two eyes, and A and B represent points on the subject. Then, angles LAR and LBR are defined as absolute parallaxes, and (angle LAR-angle LBR) is defined as a relative parallax of the point A to the point B. Hereinafter, the term “relative parallax” is simply referred to as “parallax”.
Therefore, a prism 3D camera that separates a light ray output from a subject and captured by a single video camera into left and right rays using a prism has been developed (refer to, for example, Patent Document 1).